Neuroblastoma is one of the most common malignant neoplasms in children. The prognosis for neuroblastoma patients over 1 year of age with advanced disease remains poor in spite of aggressive anti-tumor therapy. N-myc amplification is often detected in such cases, while it is hardly detected in the patients less than 1 year of age. It is still unknown which genomic aberration occur in the neuroblastoma less than 1 year of age. The purpose of this research is to investigate which oncogene is responsible for tumorigenesis of neuroblastoma.ras p21 expression was analyzed by using immunohistochemical techniques. Prognosis of the ras p21 expression positive patients was significantly good compared with that of the negative ones. The patient with N-myc positive expression showed poor prognosis In contrast, N-myc negative expression did not necessarily suggest a good prognosis. In these cases, ras-p21 expression suggested a good prognosis.Tumor suppressor gene p53 expression was analyzed by using immunohistochemical techniques and genomic mutation was analyzed by using PCR-SSCP method. Rate of p53 expression positive case was low and no genomic mutation was detected. It is suggested that p53 is not related to the tumorigenesis in neuroblastoma.